1. Field of the Invention
The present invention relates to an on-line apparatus for measuring the flash point of a petroleum intermediate fraction such as kerosene during the distillation of crude oil, and it also relates to a method for controlling the flash point of the petroleum intermediate fraction by the utilization of the measured value obtained by the abovementioned measuring apparatus.
2. Description of the Prior Art
With regard to components of a gasoline fraction and an intermediate fraction such as kerosene of petroleum, their boiling points are continuously distributed, and therefore when these components are taken out from the crude oil by distillation, kerosene is stripped or heated with steam to vaporize volatile components therefrom, which volatile components are then delivered into a gasoline fraction, whereby the flash point of kerosene is adjusted.
In this case, if the flash point of kerosene is measured by an on-line system, the amount of the steam, for example, used for heating or stripping kerosene can be regulated on the basis of the measured value, so that the flash point can be stably maintained. However, such an on-line measuring apparatus has not been developed yet. Consequently, in general, kerosine is first sampled and its flash point is then measured directly on an off-line system, and the amount of the steam is controlled with the aid of operational experience making reference to a measured value. Accordingly, the accurate control of the steam amount to be used is difficult owing to time lag and the like. It is thus necessary to make a large allowance for the safe control, which obstructs the mass production of kerosene.
In a conventional known method for directly measuring a flash point by an on-line system, a certain amount of a liquid to be measured is first sampled, and a spark is emitted through a gaseous phase above the liquid during heating in order to inflame the gas. At this time, the occurred change is confirmed and measured by detecting the generation of sound or light.
In this method, since the liquid to be measured is sampled at certain time intervals, the continuous measurement is impossible. This conventional method is substantially identical with the off-line system.
Furthermore, there is known another method for indirectly measuring a flash point in which for example, a specific gravity or viscosity is measured and the flash point is then calculated from the interrelation between this factor and the flash point. In this case, needless to say, an on-line device for measuring the specific gravity or viscosity is required, and the measurement accuracy of the flash point depends upon the performance of the measuring device.
As discussed above, in a crude oil distillation process, any convenient and reliable device and method for detecting the flash point of the petroleum intermediate fraction such as kerosene by a continuous on-line system has not been heretofore established.